The present invention relates to a method for inducing reproducible transient infertility or sterility in a mammal by inducing in that mammal antibodies directed to proteins found in the zona pellucida of that mammal's oocytes. The invention also relates to purified, isolated DNA sequences encoding the zona pellucida proteins herein designated "ZPA" and "ZPB" and "ZPC" from various mammalian species. The invention is further directed to pharmaceutical compositions capable of inducing antibody production in a subject mammal.
The zona pellucida (ZP) is a complex matrix surrounding the mammalian oocyte, formed of glycoproteins secreted by ovarian cells. Zona pellucida glycoproteins perform a variety of functions. For example, the mouse ZP proteins previously designated ZP2 and ZP3 are complexed into long filaments which are cross-linked by the protein designated ZP1 in the ZP matrix providing structural integrity to the matrix. Wassarman, P. M., Annu. Rev. Biochem. 57:415-442 (1988). In addition to its structural role, mouse ZP3 has been shown to be a sperm receptor in the ZP matrix. Bleil, J. P. and Wassarman, P. M., Cell 20: 873-882 (1980). Following binding of sperm to ZP3 and the subsequent induction of the sperm acrosome reaction on the surface of the ZP, ZP2 acts as a secondary sperm receptor that is necessary for the maintenance of sperm binding to the egg. Bleil et al., Dev. Biol. 128: 376-385 (1988). Because of its role in the maintenance of the oocyte and in sperm-oocyte interactions, the ZP represents a logical target for design of contraceptive agents which interfere with the fertilization process.
Various groups have undertaken an immunological approach in attempts to interfere with ZP functions and thus to decrease fertility in immunized animals. See, Dunbar et al. In: International Congress on Reproductive Immunology. T. Wegman and T. Gills (eds.). London: Oxford Press, pp. 505-528 (1983); and Dunbar et al. In: Mechanisms and Control of Animal Fertilization. J. Hartman (ed.) Academic Press, New York, pp. 139-166 (1983). These studies showed that active immunization of mammals with ovarian homogenates decreased fertility. However, the large number of components in such homogenates made the identification of antigens responsible for the decrease in fertility nearly impossible. In addition, the use of such a complex mixture creates a potential for unwanted and potentially harmful side-effects.
Research by various investigators using chromatographic methods including SDS polyacrylamide gel electrophoresis (PAGE) and high pressure liquid chromatography (HPLC) have resulted in the identification of numerous zona pellucida proteins from a variety of mammalian species. Data compiled by Timmons and Dunbar in "Perspectives in Immunoreproduction: Conception and Contraception"; pp. 242-260, Mathur, S. and Fredericks, C. M. eds.; New York, Hemisphere Publishing Co (1988), as described below, illustrate examples of zona pellucida proteins that have been characterized.
Zona pellucida proteins isolated from pig include: PZI, a 40-110 kD protein isolated by Dunbar et al., Biol. Reprod. 24:1111 (1981); PZII, a 70-110 kD protein, PZIII, a 95-118 kD protein, and PZIV, an 18-25 kD protein, all isolated by Dunbar et al., Biol. Reprod. 32:619 (1985); 90K, a 89-119 kD protein, 65K, a 61-83 kD protein, 55K, a 47-66 kD protein, and 25K, an 18-26 kD protein, all isolated by Hedrick, J. L. and Wardrip, N. J. Biochem. 157: 63 (1986); ZP1, an 82-118 kD protein, ZP2, a 58-96 kD protein, ZP3 (PPZA), a 40-74 kD protein, and ZP4, a 21 kD protein, all isolated by Subramanian et al., Biol. Reprod. 24:933 (1981); 87K (ZP1/ZP2), a 77-97 kD protein, 58K, a 40-70 kD protein both isolated by Yurewicz et al., Biol. Reprod. 29: 511 (1983); deglycosylated PZI, a 35 kD protein; PZII, a 55 kD protein; and PZIII, an 80 kD protein all isolated by Skinner and Dunbar as described in Immunological Approaches to Contraception and the Promotion of Fertility, G. P. Talwar (ed.) New York: Plenum pp. 251-268 (1986); and deglycosylated ZP3 having a molecular weight of 45 kD isolated by Sacco et al., J. Reprod. Fertil. 76:575 (1986).
Isolated rabbit zona pellucida proteins include: RZI, RZII, and RZIII, having molecular weights of 68-125 kD, 80-100.5 IcD, and 100-132 kD respectively, all isolated by Dunbar et al., Biol. Reprod. 24:1111 (1986); ZP1, ZP2, and ZP3 having molecular weights of 100-118 kD, 83-110 kD, and 80-92 kD respectively, all isolated by Sacco et al., Proc. Soc. Exp. Biol. Med. 167:318 (1981); deglycosylated RZI, and RZII having molecular weights of 65 kD, and 80 kD respectively, both isolated by Skinner and Dunbar and described in Immunological Approaches to Contraception and Promotion of Fertility. G. P. Talwar (ed.). New York: Plenum, pp. 251-268 (1986); and deglycosylated RZIII, a 90 kD protein isolated by Timmons and Dunbar, Biol. Reprod. 36: 1275 (1987).
A number of mouse zona pellucida proteins have been isolated including: ZP1, ZP2, and ZP3 having molecular weights of 200 kD, 120 kD, and 83 kD respectively, all isolated by Bleil and Wassarman Dev. Biol. 76:185 (1980); and ZP1 and ZP2 having molecular weights of 166-122 kD and 90-92 kD respectively, isolated by Sacco et al., Proc. Soc. Exp. Biol. Med. 167: 318 (1981). The differences in the molecular weights of mouse ZP1 and ZP2 as reported by Bleil et al. and Sacco et al. may be due to the fact that Bleil used 2D-PAGE under non-reducing conditions while Sacco used 2D-PAGE under reducing conditions.
The cat zona pellucida proteins CZI and CZII were isolated by Maresh and Dunbar J. Exp. Zool. 244:299 (1987) and have molecular weights of 50-110 kD and 90-110 kD respectively.
Maresh and Dunbar J. Exp. Zool. 244:299 (1987), have also isolated the dog zona pellucida proteins DZI, DZII, and DZIII which have molecular weights of 50-110 kD, 70-95 kD, and 90-100 kD respectively.
Sacco et al., Proc. Soc. Exp. Biol. Med. 167:318 (1981) described squirrel monkey ZP1, ZP2, ZP3, and ZP4 having molecular weights of 63-78 kD, 63-70 kD, 47-51 kD, and 43-47 kD respectively. In the same publication Sacco et al. described human ZP1, ZP2, and ZP3 having molecular weights of 80-120 kD, 73 kD, and 59-65 kD respectively.
To date, few mammalian zona pellucida genes or proteins have been isolated and sequenced. None has been successfully used to produce an effective immunocontraceptive. A lack of consensus among those of skill in the art regarding the number and characteristics (e.g. molecular weight) of proteins present in the zona pellucida of various mammalian species, and difficulties in purifying these heavily glycosylated proteins have hampered attempts to utilize zona pellucida proteins to produce an effective immunocontraceptive with predictable function.
A number of groups have had success in cloning cDNAs or genes encoding various mammalian zona pellucida proteins.
Ringuette et al., Dev. Biol., 127:287-295 (1988) and Liang et al., Mol. Cell. Biol., 10:1507-1515 (1990), reported cloning of mouse DNA encoding zona pellucida proteins ZP3 and ZP2, respectively. The clones were obtained by screening mouse cDNA libraries with anti-ZP3 and anti-ZP2 antibodies. No sequence homology was found between mouse ZP3 and ZP2.
Ringuette et al., Proc. Natl. Acad. Sci. USA, 83:4341-4345 (1986), reported isolation of a partial cDNA clone for mouse ZP3, which clone hybridized with total genomic DNA of mouse, rat, dog, cow, and human, but not with pig or rabbit genomic DNA unless the hybridization was performed at very low stringency. The full length ZP3 cDNA characterized by Ringuette Dev. Biol. 127:287-295 (1988) represents a germ-line specific mRNA having relatively short 5' and 3' untranslated regions and an open reading frame of about 1317 nucleotides with an additional 200-300 nucleotide poly-A tail. Ringuette also found that rat, rabbit, dog, and cow ovary transcribes mRNA which hybridized to the mouse ZP3 cDNA and that the ZP3 transcripts had similar molecular weights. Liang et al. Mol. Cell. Biol., 10:1507-1515 (1990), showed that the nucleic acid and deduced amino acid sequence of ZP2 is distinctly different from that of ZP3 although it had the same short motif of 5' and 3' untranslated regions. The ZP2 mRNA is reported to have single open reading frame of 2,139 nucleotides which codes for a polypeptide of 80,217 Daltons representing 713 amino acids.
Chamberlin and Dean, Dev. Biol. 131:207-214 (1989) and Kinloch, R. A. et al., Proc. Nat. Acad. Sci. USA, 85:6409-6413 (1988) have reported the cloning of the mouse ZP3 gene. The mouse ZP3 gene is reported to have 8 exons and 7 introns in a transcription unit of 8.6 kbp.
Kinloch et al., Dev. Biol. 142:414421 (1990), reported cloning of hamster genomic ZP3 DNA from a hamster genomic DNA library screened with mouse ZP3 DNA as a probe. The hamster ZP3 gene has a transcription unit of 7900 nucleotides and was found to contain 7 introns and 8 exons. The hamster ZP3 protein is approximately 81% homologous to mouse ZP3 protein. The hamster transcript contained 1266 nucleotides, six less than mouse ZP3 mRNA.
Chamberlain and Dean, Proc. Natl. Acad. Sci. USA 87:6014-6018 (1990), reported the cloning of human ZP3 from a human genomic DNA library using mouse ZP3 cDNA as a probe. The human ZP3 gene is composed of 8 exons in a transcription unit of 18.3 kbp. The exons are almost identical in size to the eight exons of mouse ZP3 and the nucleotide sequence of the coding region is 74% homologous. The human ZP3 transcript is very similar to mouse ZP3 mRNA. Both have short 5' and 3' untranslated regions, and both have a single open reading frame of 1272 nucleotides that encodes a 424-amino acid protein.
U.S. Pat. No. 4,996,297, to Dunbar, reported the isolation of three rabbit zona pellucida clones encoding rabbit ZP1 and ZP2 proteins, using anti-ZP1 and anti-ZP2 antibodies as screening probes. The sequences designated as P2 and P3 in FIG. 4 of the Dunbar patent represent rabbit ZP cDNAs of 812 and 1705 nucleotides respectively.
Schwoebel et al., J. Biol. Chem. 266:7214-7219 (1991), isolated and characterized a full length cDNA (designated rc 55) encoding the 55-kD rabbit zona pellucida protein using cross-species affinity purified antisera. The protein encoded by this cDNA has some similarity to the mouse ZP2 protein described by Liang. However, comparisons of rc 55 with the mouse ZP3 protein revealed no homology.
The functional activities of the cloned ZP DNAs and their encoded proteins have not been fully characterized and neither has their potential use as immunocontraceptives been demonstrated.
In order to develop a useful zona pellucida product for use in fertility control, particularly in the form of a vaccine, it is highly desirable to purify, isolate, and characterize zona pellucida proteins from a species of an animal of interest. Because of factors such as the purity of such proteins needed for vaccine production, and the high cost and numerous problems associated with purification of these proteins, it would be highly desirable to ascertain the DNA and amino acid sequences of zona pellucida proteins of a specific species of interest. Having such known, isolated and characterized zona pellucida proteins, the function of each zona pellucida protein may be understood and a fertility control product may be designed based upon the specific functional characteristics of a particular zona pellucida protein and for a particular mammalian species.
It would be thus highly useful and desirable to provide isolated, purified, sequenced, and characterized recombinant zona pellucida proteins which would permit the development of fertility control products possessing specific reproducible effects in eliciting transient and/or permanent infertility. Such products, where used to elicit transient infertility, would desirably have long lasting effects so as to minimize the number of times the immunocontraceptive agent must be administered to maintain infertility.